Olefin polymerization catalysts are of great use in industry. Hence, there is interest in finding new catalyst systems that increase the commercial usefulness of the catalyst and allow the production of polymers having improved properties. Catalysts for olefin polymerization are often based on cyclopentadienyl transition metal compounds as catalyst precursors, which are activated either with an alumoxane or with an activator containing a non-coordinating anion.
A typical metallocene catalyst system includes a metallocene catalyst, a support, and an activator. Supported catalyst systems are used in many polymerization processes, often in slurry or gas phase polymerization processes. For example, U.S. Pat. Nos. 6,846,770 and 6,664,348 disclose catalyst compositions containing at least one metallocene, and least one activator and a support that has been fluorided using a fluoride containing compound. See also, WO 05/075525; US 2002/007023; WO 2003/025027; US 2005/0288461; and US 2014/0031504.
Metallocenes are often combined with other catalysts, or even other metallocenes, to attempt to modify polymer properties. See, for example, U.S. Pat. No. 8,088,867. Likewise, U.S. Pat. No. 5,516,848 discloses the use of two different cyclopentadienyl based transition metal compounds activated with alumoxane or non-coordinating anions. In particular, the examples disclose, among other things, catalyst compounds in combination, such as Me2Si(Me4C5)(N-c-C12H23)TiCl2 and rac-Me2Si(H4Ind)ZrCl2, or Me2Si(Me4C5)(N-c-C12H23)TiCl2 and Me2Si(Ind2)HfMe2, (Ind=indenyl) activated with activators such as methylalumoxane or N,N-dimethyl anilinium tetrakis(pentafluorphenyl)borate to produce polypropylenes having bimodal molecular weight distributions (Mw/Mn), varying amounts of isotacticity (from 12 to 52 weight % isotactic PP in the product in Ex 2, 3 and 4), and having weight average molecular weights over 100,000, and some even as high as 1,200,000 for use as thermoplastics. See also, U.S. Pat. Nos. 4,701,432; 5,077,255; 7,141,632; 6,207,606; 8,598,061; Hong et al. in Immobilized Me2Si(C5Me4)(N-t-Bu)TiCl2/(nBuCp)2ZrCl2 Hybrid Metallocene Catalyst System for the Production of Poly(ethylene-co-hexene) with Psuedo-bimodal Molecular Weight and Inverse Comonomer Distribution, (Polymer Engineering and Science—2007, DOI 10.1002/pen, pages 131-139, published online in Wiley InterScience (www.interscience.wiley.com) 2007 Society of Plastics Engineers); US 2012/0130032; U.S. Pat. Nos. 7,192,902; 8,110,518; 7,355,058; 5,382,630; 5,382,631; 8,575,284, 6,069,213; Kim, J. D. et al., J. Polym. Sci. Part A: Polym Chem., 38, 1427 (2000); Iedema, P. D. et al., Ind. Eng. Chem. Res., 43, 36 (2004); U.S. Pat. Nos. 6,656,866; 8,815,357; US 2004/259722; US 2014/0031504; U.S. Pat. Nos. 5,135,526; 7,385,015; WO 2007/080365; WO 2012/006272; WO 2014/0242314; WO 00/12565; WO 02/060957; WO 2004/046214; WO 2009/146167; and EP 2 374 822 A.
There is still a need in the art for new and improved catalyst systems for the polymerization of olefins, in order to achieve increased activity or specific polymer properties, such as high melting point, high molecular weights, to increase conversion or comonomer incorporation, or to alter comonomer distribution without deteriorating the resulting polymer's properties.